Lawn maintenance vehicles such as riding lawn mowers or lawn tractors typically use a clutch to transfer rotational power from the power take-off (otherwise known as the “PTO”), which is a rotatable drive shaft that extends from the engine. There are numerous designs and configurations for drive system clutching and braking mechanisms for use with lawn maintenance vehicles which may include friction-types with consumable media and non-contact-types utilizing fluids or eddy current or magnetics.
One clutching configuration is a belt clutch mechanism in which power is transmitted from the PTO to an implement with rotatable blade(s) or other devices with rotational inputs via a set of belts that are slack for de-coupling (de-clutching) from the PTO. The configuration also provides for tightening or tensioning the set of belts for coupling (or engaging) implements or other devices by way of pulleys that are then rotatably driven by the PTO and corresponding belts. Belt-type clutching mechanisms do not tolerate mis-alignment well, wherein engagement smoothness is largely dependent on instantaneous friction coefficients and component geometry. Disengagement or de-clutching generally requires a secondary mechanism to eliminate belt-pulley drag.
Another clutching configuration is a dog clutch mechanism which provides positive, non-slip engagement between components. Dog clutch mechanisms are typically used where slipping between components is not acceptable. Partial engagement of components under any significant load tends to be destructive.
A further clutching configuration is a hydraulic clutch mechanism wherein the driving and driven members are not in physical contact. Coupling is hydrodynamic and varies with the fluid properties and temperature. These clutches tend to be more expensive and physically larger than belt and dog clutches.
Yet another clutching configuration is an electromagnetic clutch mechanism in which a clutch is engaged by an electromagnet that is an integral part of the clutch assembly. Magnetic particle clutches have magnetically influenced particles contained in a chamber between driving and driven members which, upon application of direct current, causes the particles to clump together and adhere to the operating surfaces. Engagement and slippage are notably smooth. These clutches are more expensive and physically larger than other clutches, and typically require a secondary power source for engagement and de-clutching. Rate of engagement is rapid which imparts shock loads into the PTO system. These loads reduce the life of the drive system.